The bacterium belonging to the genus Clostridium is an anaerobic microbe and widely found in nature including soil, river, sea water, and intestine of a living organism, and it is also known as a bacterium which causes food poisoning or infectious diseases.
Clostridium welchii (Clostridium perfringens) as one type of the bacteria belonging to the genus Clostridium is also one of the bacteria, which cause food poisoning or an infectious disease. Clostridium welchii secretes various kinds of toxins and it is also known to cause gas gangrene, which is a lethal infection. Examples of toxins that are known to be secreted by Clostridium welchii include such as alpha-toxin (phospholipase C, name of the gene: plc), theta-toxin (hemolysin, name of the gene: pfoA), and kappa-toxin (collagenase, name of the gene: colA).
In Non-Patent Literature 1, it is described that, in Clostridium welchii, production of those toxins are positively regulated at gene level by a regulation system that is referred to as VirR/VirS system.
In response to an outer environment, gram-positive bacteria including those belonging to the genus Clostridium secrete an auto-inducer. A secreted autoinducer has an activity on a bacterium and promotes the production of a toxin. In Staphylococcus aureus as a gram-positive bacterium, a certain kind of peptide having a thiolactone structure functions as an autoinducer, and it is known to promote production of a toxin through the AgrA/AgrC system. In Non-Patent Literature 2, it is described that Clostridium welchii carries a homolog of the autoinducer peptide of Staphylococcus aureus and the homolog promotes production of a toxin through the VirR/VirS system.
In Non-Patent Literatures 3 and 4, it is described that Clostridium difficile and Clostridium botulinum, which are the bacterium belonging to the genus Clostridium, have a gene encoding the homolog of VirR and VirS.
In Non-Patent Literature 3, it is described that a bacterium belonging to the genus Clostridium such as Clostridium welchii (Clostridium perfringens), Clostridium difficile, botulinus (Clostridium botulinum) and Clostridium acetobutylicum has a gene encoding an autoinducer peptide AgrD.